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The copy protection in the Super Archiver disk (and other similar software).

The Super Archiver disk, and its copy protection, belongs to a special category.
Almost every other Atari copy protected disk was designed for standard Atari
hardware, specifically for an 810, 1050, or compatible drive. The SA however, needs
a drive modified with “The Chip”, or at least fully emulating “The Chip” (such as a
Happy drive with additional software).

There are other software and disks for custom drives. Actually, virtually every custom
drive or drive enhancement includes special software. But in almost every case the
disks are not copy protected.

The fact that the disk requires custom hardware opens a whole new world of possible
copy protections. Before elaborating in its description, let’s agree on some basic
concepts about on-disk copy protections.

The main concept of on-disk copy protection is the possibility of reliably
distinguishing an original from a user made copy
using the standard user setup.
The last part of the last sentence is the key here. If we are releasing protected
software, we can't take the disk to a lab for a very detailed analysis. We are limited
by whatever analysis is possible at runtime on the user machine.

As most people know, the Atari drive is a smart device and has a high level interface
only. You can’t do much more than a read a logical sector, write a logical sector or
format a whole disk. The protection analysis is severely limited by this software
interface. The consequence of this is that the copy protections that are possible on
the Atari are also limited. Most other systems have a lower level interface available,
and then the variations and complexity of copy protections is much broader.

But wait a minute. Didn’t we say the SA disk runs on a custom drive, which has a
custom low-level protocol? Exactly, so the SA protection is not limited by the standard
Atari drive interface. This is the reason that the SA disk can use copy protections
that “normal” Atari software cannot.



So what is the protection on the SA disk?

If we analyze the SA disk we see that track 1 and tracks 30 to 38 have a big number
of sectors (up to 42). Most people think that this is the protection that the SA itself
can’t copy (or the Happy for that matter). But this is just a decoy, it’s not the real
protection.

The real protection is on tracks 3 to 6. Most disk analysis tools (including SA itself)
cannot even see the protection on these tracks. These tracks have weak bits on one
of the sectors headers (a weak header). A weak header doesn’t make any sense in a
normal Atari drive, because there is no way to detect it. But “The Chip” interface
allows reading all the headers on a specific track. So it is rather simple to read the
headers on one of those tracks twice or more times, to be able to detect the
protection at runtime.


There is a common misconception that the SA disk was created using a Unix system.
This doesn’t make much sense. In first place Unix is an operating system. The
possibility of writing (or not) a specific protection doesn’t usually depend on the
operating system, but on the available hardware.

Although I cannot be 100% sure, I believe that the SA disk, as all other C.S.S.
protections was created in an Atari drive. In the specific case of the SA disk I believe
it was written in a modified 1050 using a custom version of the SA hardware (which
was also manufactured by C.S.S.). I’m not very familiar with the SA hardware, so I
cannot be very specific. But a custom version of the software, and/or the firmware
was likely enough to produce this protection.

There are a couple other software titles that fall in the same category as the SA. The
ones I know are Scan-It (only later versions are protected) also by C.S.S., and
Archiver for the Happy 810 by Spartan. As you can see, they are all Chip/Archiver
related. They both have protections that make sense only in a custom drive.



VAPI and the SA

VAPI currently has limited support for the SA and the other software mentioned. The
tools can image the disk, and with the right hardware can also write them back. You
cannot use them, however, under emulators or with a SIO2PC/Ape application. This
will require, at least, emulating The Chip firmware, which is currently not implemented
(we do plan to eventually implement it). Note that some emulators already have
limited emulation of The Chip, but not at the level that is required for this purpose.

Again, supporting the SA and the Archiver software is in our plans. Supporting Scan-
It, if we want a true emulation, would be much more difficult. It would require
emulating the 6502 CPU inside a Happy drive. We might eventually reach there,
although there is probably not much need. In this case, there is really no need
because fully emulating The Chip avoids the need of using Scan-It altogether.
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